The primary objectives are: a) to define the optimal conditions for conjugating amanitin diazobenzoylglycylglycine to anti-DNP rabbit IgG and retaining maximal hapten binding activity. A comparison of conditions for conjugation using water soluble carbodiimide (EDC) and N-hydroxy-succinimide esters (NHS) with ADGG will be made, b) to examine conjugates of ADGG and anti-DNP IgG which retain significant affinity for free hapten for their ability to inhibit the in vitro and in vivo proliferation of murine lymphocytive leukemia cells (EL-4) which have been coated with varying quantities of the hapten analog, TNP, c) to determine the fate of the amanitin versus the antibody carrier for in vitro inhibition studies with ADGG anti-DNP IgG conjugates in which the ADGG moiety has been labeled with 3H and the IgG moiety with 125I, d) to prepare and characterize conjugates of ADGG and monoclonal IgG directed against Thy 1.2 antigens to define the relative affinity and number of binding sites on EL-4 cells (Thy 1.2 plus) and other murine lymphoma lines containing little if any Thy 1.2 antigen, i.e. C1498 and S49, and e) to determine the capability of ADGG-anti Thy 1.2 IgG to specifically block the in vitro and in vivo proliferation of Thy 1.2 containing cells (EL-4) and Thy 1.2 deficient cells (C1498 and S49).